Christie’s puts under the hammer next week the largest fancy vivid pink diamond that the famed auction house has ever sold, expecting to fetch $30 million to $50 million for the nearly 19-carat, rectangular-cut gemstone.

The “Pink Legacy” will be the standout offering at Christie’s fall jewelry auction in Geneva on Tuesday.

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The stone once belonged to the Oppenheimer diamond family, and Christie’s says it qualifies as a Type IIa diamond — the most chemically pure stones with little if any nitrogen. It says fancy vivid pink diamonds over 10 carats are “virtually unheard of” in salesrooms.

Christie’s sale kicks off two days of jewelry auctions in Geneva. On Wednesday, Sotheby’s will auction jewelry once owned by French Queen Marie Antoinette that hasn’t been seen in public for 200 years.